Grinding wheel



March 18, 1958 I F, w. LINDBLAD I 2,826,878

GRINDING WHEEL Filed Aug. 50, 1955 United States Patent This inventionrelates to grinding wheels which are suit able for grinding laminatematerials and other materials which produce uneven wear on the face ofthe grinding wheel.

In the grinding of the edges of safety glass with a "conventionalgrinding wheel, a grooveis often Worn in the central portion of thewheel. This changes the resulting contour of the ground edge of theglass being worked upon, which is objectionable. In addition, thisnecessitates a replacement of the wheel before the major portion of'theabrasive wheel rim has been used.

'The uneven wear on the grinding wheel is perhaps initiated by thesmudging of the plastic lamina of the safety glass, softened by the heatof friction, during grinding. Abraded material, including glassparticles and, perhaps, powdered parts of the wheel that have been wornaway, adhere to the tacky portions of the lamina and thereby produce anabrading compound embedded in the plastic which tends to wear away thegrinding wheel atthe place where the plastic lamina is located in thesafety glass. Regardless of whether or not that is the, explanation forthe uneven wear on the'grinding wheel, the fact is that uneven wear doestake place, and is objectionable.

his one of the objects of this invention to provide a grinding wheel inwhich the wear on the wheel is more evenly distributed when the wheel isused for laminate bodies wherein the laminae have varying abrasivequalities, or where other conditions exist which ordinarily provide foruneven wearing of grinding wheels of .the type heretofore used.

The abrasive rims of grinding wheels are often formed of a number ofcircumferentially spaced abrasive segments wherein opposed faces ofadjacent segments are spaced apart to leave clearance spaces for removalof ground particles from the grinding surface of the wheel. Theclearance spaces create agitation of the air or coolant which-aids inremoval of the ground particles from between the segments. Thedifiiculty with this design is that vibration and chattering of thegrinding wheel frequently results, perhaps due. to the intermittentcontact between the grinding wheel and the work piece.

It is therefore another object of this invention to provide a grindingwheel wherein the grinding surface of the wheelis designed to maintaincontinuous contact with a work piece, while yet providing a number ofclearance spaces for removal of ground particles from the grindingsurface of the wheel. a

In accordance with a preferred form of the invention,.

the abrasive rim of the grinding wheel is formed of a number ofsubstantially identical, separate abrasive'segments which are in contactalong a portion of their width, and which are separated along otherportions of their width to provide clearance spaces for the passage ofground particles in the periphery of the grinding wheel. For particulargrinding applications where uneven wearing has been a problemheretofore, spacing of the spaced portions of the abrasive-segmentsare-such that the over-' The grinding wheel there shown is similar tothe grinding 2,826,878 Patented Mar. s, 1958 all angular extent ofdifferent axially spaced portions of the periphery of the grinding wheelvary in accordance with the abrasive qualities of the portions of thework piece with which they are to make contact. The result is that thesame amount of material is removed from each portion of the body beingground for each revolution of the grinding wheel, resulting in evenwearing of the grinding wheel. I

These and other objects, advantages and features of the invention willbecome apparent upon making reference to the specification to follow,taken in conjunction with the drawings wherein:

Fig. 1 is an elevational view, partly broken away, of a grinding wheelincorporating features of the invention;

Fig. 2 is an edge view of the grinding wheel of Fig. 1;

Fig. 3 is an enlarged fragmentary side view of a portion of the grindingwheel periphery of Fig. l;

Fig. 4 is a fragmentary enlarged end view of a portion of the grindingwheel periphery of Fig. 1;

Fig. 5 is a section through a portion of the grinding wheel periphery,taken along section line 5-5 in Fig. 4;

Fig. 6 is a fragmentary edge view of a portion of a modified abrasivegrinding wheel;

Fig. 7 is a section through the portion of the grindin wheel of Fig. 6,taken along section line 77;

Fig. 8 is a fragmentary edge view of a portion of another modified formof grinding wheel; and

Fig. 9 is an end view of a still further modified form of grindingwheel.-

. In the drawings like reference numerals indicate like elementsthroughout.

The grinding wheel 1 shown in Figs. 1 through 5 comprises a number ofseparate, abutting, abrasive segments 3 assembled to form a wheel-likegrinding surface. The segments are secured together by a frame 5 whichincludes a pair of spaced, circular opposed disk sections 77 whichdefine therebetween a peripheral outwardly facing channel 9 whichreceives the abrasive segments 3. The abrasive segments are held inplace within the channel 9 as by pins 11 which pass through the wheeldisks 7-7 and through the abrasive segments. The wheel frame is securedto a hub 13 which is connected to a shaft 14 suitably journalled forrotation in any conventional manner.

The opposed ends of the abrasive segments are beveled to form a seriesof discontinuities 15 in the abrasive surface of the grinding wheelbetween-adjacent abrasive segments. In Figs. 1 to 5, the beveling of theedges of each segment leaves a flat 17 which lies in a plane thatincludes the axis of rotation of the shaft 14. The flat 17 at each endof each segment is abutted and overlaid bythe corresponding flat of theadjacent segment along the entire thickness of the segment. The opposedradial surfaces of the abrasive wheel segments lie along radial lines18. The angle of the radial line 18 with respect to a plane at rightangles to the axis of rotation of the wheel determines the rate ofdiminution of the periph-- eral extent of the wheel along sectionsspaced axially from the flat 17. The grinding wheel 1 having the V-shaped discontinuities 15 will evenly grind a body which In thepreferred form of the invention, adjacent siegments 3 are in contact toprovide a continuous grinding wheel surface which maintains continuouscontact with the body to be ground, to eliminate chattering or unduevibration of the grinding wheel.

Figs. 6 and 7 show a modified form of grinding wheel-l p.osing:faces; ofthe segments are beveled through to the. center line of the segments sothat adjacent segments make merely a line contact. Successive axiallyspaced segments on opposite sides of the center of the rim are thereforeincontact with the work piece for gradually decreasing lengths. of timefor each revolution of the wheel.

Fig. 8 shows a still further modified form of grinding.

wheel. in. having abutting segments 3a (which correspond to therespective segments 3 of Fig. 1) with generally V-shapedend faces 20aforming diamond-shaped discontinuities lie between the segments. Theend. faces are beveled. to. provide axially spaced peripheral rimportions. of. the samev respective angular extents-as the wheel. rim isevenly worn away. it can be seen that the abrasive rim of thewheelmaltes contact with a work surface for progressively greater.amounts of time per revolution proceeding outward from the centerportion thereof. This embodiment is used to grind a surface where theabrasive forces applied to the grinding wheel are greatest at theextremities of the wheel rim and gradually diminish toward the medialportion thereof.

In the modified form of wheel 1b in Fig. 9, the ends of each of thesegments 3b (which correspond to the segments 3 of Fig. 1). haverectangular projecting portions 21 in the medial regions thereofproviding rectangular discontinuities 15b15b on the outside of the wheelrim. Thus, the medial portion of the rim makes contact with the worksurface for a greater period of time than the outer portion of the rim.

In each of the different embodiments herein described the grinding wheelincludes a series of arcuate abrading segments, for instance,twenty-four segments secured together as in Fig. 1. In each instance,adjacent segments are in contact with one another along a line or aplane that extends radially of the center of rotation of the grinder. Ineach instance there is separation of adjacent grinding segments if asection is taken at right angles to the axis ofrotation of the wheel andat a location spaced axially of the place of contact of the adjacentsegments. In each instance the separation tapers in a direction radiallyof the wheel so that in any planar section, taken in a plane at rightangles to the axis of rotation of the wheel; the ratio of the sum of theperipheral extents of the grinding segments to the sum of the peripheralextents of the spaces between the grinding segments remains con stantas' the grinding segments are worn down. The arcuate extent of thegrinding surface varies in different spaced planes taken through thegrinding wheel at right angles to the axis of rotation thereof, thevariation being in proportion to the differences in the amount ofabrading action that would take place upon the wheel itself at differentaxially spaced portions thereof if the segments were in contact with oneanother throughout their full axial width.

In compliance with the requirements of the patent statutes Ihave hereshown and described a few preferred embodiments of my invention. It is,however, to be understoodthat the invention is not limited to theprecise constructions here shown, the same being merely illustrative ofthe principles of the invention. What I consider new and desire tosecure by Letters Patent is:

1. A grinding wheel for use in grinding a work piece wherein differentportions thereof that are ground simultaneously have different wearingeffects on the abrasive of the wheel, said wheel comprising an abrasiverim having different abrading wheel portions that abrade the differentportions of the piece to be ground simultaneously. said abrading wheelportions being respectively of different circumferential extents lyingin. a common plane with and transversely of the periphery of said rim,and the ratios of said circumferential extents being a function. of

i '4 the ratios of the wearing effects of the piece ground at saiddifferent portions thereof.

2. A grinding wheel having an abrasive rim with discontinuities formedin the abrading face thereof having progressively different totalpcripheral angular extents at different portions of the rim, so that onegrinding section of the wheel makes contact with said body for a longertime in a revolution of the wheel than another grinding section.

3. A grinding wheel such as is defined in claim 2 wherein the section ofthe wheel that makes maximum contact with the work during eachrevolution of the wheel is the portion that lies in a plane located atright angles to the axis of rotation of the wheel and midway between theedges of the abrading face of the wheel.

4. A grinding wheel for grinding a body where the abrasive effect of thebody on the wheel. varies across the abrading face of the wheel,comprising an. abrasive rim: having a number of separate, identical,peripheral segments in spaced relation about the axis of rotation of thewheel and adapted to make successive contact with a portion of the'bodyto be ground, each of'sai'd segments having axially. spaced portionswhich vary in overall: angular extent. about the wheel axis so thatdifferent corresponding axial sections of the wheel are in contact witha given portion of said body for different lengthsof time for eachrevolution of the wheel.

5. A grinding wheel. for grinding a body where. the abrasive effect ofthe body on the wheel varies across the abrading face of the wheel,comprising a rim of abrasive material havingv axially spaced abradingsections.

which have. different respective overall abrading qualities, adjacent.ones of said sections being in contact along, only a portion of theiropposite ends the average abrasive effect per inch of circumferentialextent thereof being respectively different and a function of the.abrasive effect ofthe. portions of said body which are contactedthereby.

6. A grinding wheel including an abrasive rim which has a continuousabrasive portion extending completely about the axis of rotation of thewheel so that the rim maintains continuous contact with the workpiecebeing ground, and a series of discontinuous portions formed in theabrading face of the wheel which provide clearance spaces for particlesremoved from the work piece.

7. A grinding wheel. including a number of separate, abrasive, grindingwheel segments spaced about. the axis of rotation of the wheel so thatthe segments make successive contact with a work piece being ground andadjacent segments being fiush in contact along a portion of the width ofthe abrading surfaces thereof, whereby the grinding wheel is incontinuous contactwith the work piece, and a portion of adjacentsegments being spaced apart along their opposed abrading surfaces anamount to provide clearance for the passage of abraded particles.

8. A grinding wheel as defined in claim 7 further characterized in thatsaid spacedapart portion opens through opposite sides of said segmentsto produce a maximum abrasive effect in those portions of said adjacentsegments in contact with each other and diminished abrasive effectoutwardly of said contacting portions.

9. A grinding wheel as defined in claim 7 further characterized in thatsaid spaced apart portion defines a discontinuity therebetween andopening through the abrading surface at a location between the adjacentsegment portions at which they are in contact to produce a diminishedabrasive force in the medial portion of said wheel and a maximumabrasive force outwardly of the medi'al'portion.

10. A grinding wheel comprising a series of separate abrasive grindingwheel segments, means securing, the segments together to form a grindingwheel, each segment having successive peripheral abrasive portionsacross the grinding face of the wheel which fall. along the samerespective. circles as the. corresponding portions of. the

other segments, and. adjacent segments contacting each other along atleast one pair of said corresponding portions thereof and othercorresponding portions of adjacent segments being spaced apart.

11. A grinding wheel for use in grinding a work piece wherein differentportions thereof that are ground simultaneously have different wearingefiects on the abrasive. of the wheel, said wheel comprising an abrasiverim having a plurality of circumferentially spaced discontinuities inthe abrading face thereof to define therebetween abrasive portions onsaid rim, said abrasive portions being of respectively differentcircumferential extents, and theratios of said circumferential extentsbeing a function of the ratios of the Wearing effects of the work pieceground at said different extents of said portions.

12. A grinding wheel having an abrasive rim with sets of discontinuitiesformed in the abrading face thereof having different total peripheralangular extents at different portions of the rim, so that one grindingsection of 6 the wheel makes contact with said body for a longer time ina revolution of the wheel than another grinding section, the sets beingspaced from one another around the periphery of the wheel and thediscontinuities of each set being opposite one another axially of thewheel and each tapering to and ending at a point which is midway of thewidth of the wheel.

References Cited in the file of this patent UNITED STATES PATENTS875,935 Landis Jan. 7, 1908 1,422,200 Harris July 11, 1922 1,783,729Larsson Dec. 2, 1930 2,032,362 Herman Mar. 31, 1936 2,256,120 LovenstonSept. 16, 1941 2,467,878 Beth Apr. 19, 1949

